77smk

[Bottom Fodder]

I know the 77’s were made to load at mag length but when loading for single feed bolt gun do you see any advantage to loading long with less jump as for as accuracy

 

[mgdietrich]

no, they love to jump and don't seem to care. I wouldn't worry about long jumps at all.

 

[RegionRat]

In Service Rifle XTC, the 77 SMK and TMK jump for magazine length loads. That is for stages where magazine feed is required, such as the 200 yard sitting and 300 yard rapid prone stages.

However...

There is nothing that prevents them from being seated differently in a bolt gun, or from responding to seating depth in a gas gun if loaded longer.

Traditionally, the SMK 80 is used at 600 where the course is slow fire so single loading and loading long works within the rules, but here and there with shortages, some folks have tuned their SMK 77 and TMK 77 for use at the 600 yard lines to run a little better group.

 

[Bottom Fodder]

In Service Rifle XTC, the 77 SMK and TMK jump for magazine length loads. That is for stages where magazine feed is required, such as the 200 yard sitting and 300 yard rapid prone stages.

However...

There is nothing that prevents them from being seated differently in a bolt gun, or from responding to seating depth in a gas gun if loaded longer.

Traditionally, the SMK 80 is used at 600 where the course is slow fire so single loading and loading long works within the rules, but here and there with shortages, some folks have tuned their SMK 77 and TMK 77 for use at the 600 yard lines to run a little better group.

That’s the deal running very low on 80 smk with none to be found and have 6 or 700 s SMK and most places have them in stock, just wondering if I needed to add variable jump into the load development

 

[RegionRat]

That’s the deal running very low on 80 smk with none to be found and have 6 or 700 s SMK and most places have them in stock, just wondering if I needed to add variable jump into the load development

Depending on your chamber, you may end up close to just using your regular load.

There are some places (bases) I shoot that require "factory ammo" for some alleged insurance rules, blah blah blah... I am civilian so I do what I am told so I don't create any trouble for my hosts. I have shot 77 TMK at mag length on the long line. While I have not cleaned with that I have shot 199. I missed a let off and it didn't cut the line, so that was my fault not the load.

The 77 TMK really splits the BC difference between the 77 and 80, so you might find those will work for you even at magazine length.

 

[jlorenzo]

Anyone know how much a 77 is jumping from a Pmag in a wylde chamber?

Also looking at loading some 77s longer for a bolt gun to fit a little more powder. They wont seat out as long as something like an ELD because of the ogive.

 

[Jeff Porter]

I played with that a few years back and really did not get any significant improvement over mag length jump with that bullet. Some of my best scores in XTC higpower at 600 were with mag length Lapua 77's.

 

[jlorenzo]

I played with that a few years back and really did not get any significant improvement over mag length jump with that bullet. Some of my best scores in XTC higpower at 600 were with mag length Lapua 77's.

I'm struggling to get Sierra 77s to shot clover leafs in my gas gun. I had hoped a white oak barrel would get me there,(18" SPR 1:7 wylde) and I did see some improvement but not all touching. Maybe its just me though, I think I suck at shooting gas guns for groups. I did notice things seemed to tighten up a touch loading a bit shorter than mag length. Havent had enough time to really figure it out yet. Thinking of getting a heavier 20" and selling the 18" SPR.

 

[Jeff Porter]

I'm struggling to get Sierra 77s to shot clover leafs in my gas gun. I had hoped a white oak barrel would get me there,(18" SPR 1:7 wylde) and I did see some improvement but not all touching. Maybe its just me though, I think I suck at shooting gas guns for groups. I did notice things seemed to tighten up a touch loading a bit shorter than mag length. Havent had enough time to really figure it out yet. Thinking of getting a heavier 20" and selling the 18" SPR.

Absolutely try shortening mag length ammo if you have issues with grouping. As counter intuitive as it seems, with Hornady 75's and Nosler 77's in my 20" WOA Wylde chambers i get tighter rounder groups with these bullets seated to 2.235" instead of trying to drag the tips on the magazine. I am actully jumping Berger 80.5's 0.130" for mid range matches in my gas gun SR.

Shootng a gas gun off of a bench from a rest bags or bipod is not the same as shooting a bolt gun. So many moving parts the position of the fore end on the rest or bag and the presures you apply to a bipod and even your cheek weld have to be the same every time to minimize a group.

I actually shoot better groups slung up on the ground with a sand bag in front of my non firing hand with an AR.

 

[RegionRat]

I'm struggling to get Sierra 77s to shot clover leafs in my gas gun. I had hoped a white oak barrel would get me there,(18" SPR 1:7 wylde) and I did see some improvement but not all touching. Maybe its just me though, I think I suck at shooting gas guns for groups. I did notice things seemed to tighten up a touch loading a bit shorter than mag length. Havent had enough time to really figure it out yet. Thinking of getting a heavier 20" and selling the 18" SPR.

You are doing good.

If we take a step back for a moment... a gas gun can present more challenges to hitting state of the art accuracy and precision than a bolt gun. Having the expectation that a sling support should hold the SR X-Ring in the hands of a High Master is fair, but keep in mind what an X-Ring diameter really is for an SR target.

Now, taking that same rig and by adding bag riders and putting it in the hands of a High Master F-Class shooter, and then putting it in perspective compared to a match bolt rig, do we really expect the gas gun to equal the bolt gun? With those bag rests come targets with half the X ring size. Yet has been done.

It is possible to get one under 1/2 MOA for 20 shot strings in the right hands and under testing conditions, but even at 600 yards you rarely hear about cleans high X counts with a SR rifle in a Mid Range F-Class match. That is to say it is possible and has been done, but not by the average shooter.

Trying for a rare feat should be kept in perspective. Clover leaf groups out of a SPR or SR bbl at 100 yards is possible but even grouping under the 5s for 20 shot strings is an accomplishment with 77 SMK or TMK from the magazine. That is margin against the normal target for those applications and pushing the state of the art against an F-Class target.

If it was easy, we would see more gas guns in F-Class Mid Range matches and we would have to raise the bar on what it means to be High Master. YMMV

 

[jlorenzo]

You are doing good.

If we take a step back for a moment... a gas gun can present more challenges to hitting state of the art accuracy and precision than a bolt gun. Having the expectation that a sling support should hold the SR X-Ring in the hands of a High Master is fair, but keep in mind what an X-Ring diameter really is for an SR target.

Now, taking that same rig and by adding bag riders and putting it in the hands of a High Master F-Class shooter, and then putting it in perspective compared to a match bolt rig, do we really expect the gas gun to equal the bolt gun? With those bag rests come targets with half the X ring size. Yet has been done.

It is possible to get one under 1/2 MOA for 20 shot strings in the right hands and under testing conditions, but even at 600 yards you rarely hear about cleans high X counts with a SR rifle in a Mid Range F-Class match. That is to say it is possible and has been done, but not by the average shooter.

Trying for a rare feat should be kept in perspective. Clover leaf groups out of a SPR or SR bbl at 100 yards is possible but even grouping under the 5s for 20 shot strings is an accomplishment with 77 SMK or TMK from the magazine. That is margin against the normal target for those applications and pushing the state of the art against an F-Class target.

If it was easy, we would see more gas guns in F-Class Mid Range matches and we would have to raise the bar on what it means to be High Master. YMMV

All very good points. I just know a semi can shoot better than mine is currently shooting. I have no expectations of half MOA 20 round groups. Just tighter than this. I think some of these may be me/rear bag related. This is off a magpul bipod as well. The two smaller groups I would be happy with if they were consistent in size and placement. This is a new barrel and I haven't done a ton of work with it so hopefully I can tighten things up.

 

[jelenko]

Well, the 23.2 group looks less the 3/4 MOA.

 

[jrh84]

All very good points. I just know a semi can shoot better than mine is currently shooting. I have no expectations of half MOA 20 round groups. Just tighter than this. I think some of these may be me/rear bag related. This is off a magpul bipod as well. The two smaller groups I would be happy with if they were consistent in size and placement. This is a new barrel and I haven't done a ton of work with it so hopefully I can tighten things up.

I've got a buddy that uses a Magpul bipod...I think you might have better luck if you try a Harris or Harris-style clone bipod. The Magpul is nice, but it doesn't go low enough for my liking, and seems to be more wobbly than a Harris style. I haven't personally messed with one enough to really sort it out.

I'm not an AR accuracy guru by any means, but I do believe there's a reason why service rifle shooters generally have better results shooting slung up vs. off a bipod or rest. My theory is that there's a lot going on between the loose fit of the lower and upper and the 90 deg swing of the hammer when trigger breaks, and therefore an AR won't be accurate if shot using free-recoil (at least not in my experience) like a bolt action rifle with a super quick lock time. A tight sling helps hold everything in place between the trigger break and the primer detonation.

To me there's 4 factors to help shooting an AR from a bipod....
1. Get the bipod as low as you can and still be comfortable
2. Heavily load the bipod
3. Use a lot of cheek pressure on the stock, and mash the stock into your rear bag.
4. Use firm grip on the pistol grip (not squeezing water out of it, but enough to leave temporary marks/indentation from the checkering/texture on an A2 grip

Try smothering the thing and see if groups don't shrink a bit.

 

[RegionRat]

This is a new barrel and I haven't done a ton of work with it so hopefully I can tighten things up.

Keep the faith. You will do better once you have things figured out.

Let me ask a background question or two.

I can see your load data with 8208. My guess is that this isn't the gun based on how vast the difference is between those steps. 8208 is decent stuff, and fairly well known so I am guessing this isn't the cause but that is just a guess.

We should be able to get a reference baseline with 24.0 RE-15, Rem 7 1/2 at Mag length. or the same with 23.5 of Varget.

How would you describe your prep?

Service Rifles from WOA (and CLE) are so reliable at 200/300, that I will say that they will hold the SR target x-ring with any ammo that is at least decent. When fed good ammo, you get margin against 1 MOA. So a couple of those groups look right, but then right next to them are bad ones.

Are you experienced shooting over a bipod? Have you spent time with a different rifle that you know shoots tight over a bipod? It takes practice to master a bipod just like shooting from bag rests does.

Is it possible to have a Master or High Master shoot your rig? Sometimes that helps take the shooter off the table quickly.

It is hard to guess if we are debugging "the arrow or the Indian" yet, but keep the faith and you will get there.

 

[jlorenzo]

I really like 8208. I have had really outstanding results in my Bartlien Barrelled Tikka with it. Cleans up nicely too.

I have shot both Varget and RL15 through a different barrel but I've only shot RL15 in this gun once at a 600y any/any match, noticed with the increase in temp throughout the morning my shots climbed in elevation. Not a huge deal to compensate for if aware. I think its a good idea to try both of those again, I have both. Also want to try Tac, which shot worse that the groups I posted. When I tried it that was with Hornady 75gr bthps. I have Fed GMM AR primers, CCI 41s, 200s and some Rem 7 1/2. Only used the 41s so far.

I am pretty experienced shooting over a bipod, I am leaning more towards the rear bag being an issue. I was using a basic bag under the A2 stock. I have purchased a nice leather protektor rear bag that will hold the gun in a much more consistent manner. Some of my groups looking like they are split in two separate groups feels like a position shift to me.

Pretty firm grip on the gun, bipod loaded consistently, pulled in to the shoulder more than I do with the bolt gun. I did notice an improvement handling the gun in a more firm manner.

Brass prep is nothing fancy, LC brass matching head stamp, FL sized in a Hornady custom die, shoulder bumped .003-.004",trimmed to 1.750". I have only recently started to anneal. champfer/deburr on RCBS case prep station. Bullets seated with Hornady custom die with micrometer insert.

I am aiming to keep things simple and really am not a huge competitor. I have shot the local 600y any/any matches but that's it so far. I am liking the bolt gun for that. I am finding the Service Rifle world very intriguing lately. Most of my shooting is stationary from a bipod so the heavier 20" barrel makes more sense to me, don't mind the slight velocity bump and I think it looks better than the 18". For now I will keep working with the 18".

I just haven't had the time to really do the testing I want and side lined the gasser to focus on the bolt gun load developement. Hopefully in the next few months I find a go to load or two for the AR. I am really just a hobbyist that likes to tinker more than a serious competitor.

 

[RegionRat]

Your observation of the temp sensitive of RE-15 is valid and means you are sensitive enough to catch it, which is good. The point of bringing up RE-15 is the reliability of getting it to group well at 24 grains plus or minus a little for each gun, not to switch to it.

Varget is pretty flat temperature wise, but is also known as tipping over on the hot end without much warning. That isn't a worry if you don't load hot to begin with. Roughly 23.5 plus or minus a little trim isn't hot, but 24.5 can be on a bad day.

It does sound like your technique is part of the vertical spread. I would put you on bag riders for a load test to determine the root cause. That gets the rear squeeze bag and bipod out of the question and isolates this to the load and gun if you know how to shoot off bags. If it won't shoot off bags, then you know you have to work the gun or the load. YMMV

 

[gjcamacho]

Absolutely try shortening mag length ammo if you have issues with grouping. As counter intuitive as it seems, with Hornady 75's and Nosler 77's in my 20" WOA Wylde chambers i get tighter rounder groups with these bullets seated to 2.235" instead of trying to drag the tips on the magazine. I am actully jumping Berger 80.5's 0.130" for mid range matches in my gas gun SR.

Shootng a gas gun off of a bench from a rest bags or bipod is not the same as shooting a bolt gun. So many moving parts the position of the fore end on the rest or bag and the presures you apply to a bipod and even your cheek weld have to be the same every time to minimize a group.

I actually shoot better groups slung up on the ground with a sand bag in front of my non firing hand with an AR.

Hi, started reloading last year, all .223REM, cloning the MK262 with good results sub MOA. My barrel is a 20" SS416R and 5R rifling in .223 Wylde, believe it or not, a BCA barrel I call it the unicorn barrel because you all know the bad rap BCA gets with malfunctioning uppers From what ive seen it does like the projectile seated deeper than 2.260, I seat them at 2.250 and use 25.0 of 8208XBR. Now Im fooling around with a 6ARC upper and the learning curve is big. Slowly but surely I'll be there.

 

[Jeff Porter]

You can back down the 8208 a couple of grains and still have a great shooting 77 gr load. 25.0 is a stout load of 8208. I don’t go over 23.5 without a plus 2 gas system and a heavy buffer.

 

[jlorenzo]

Hi, started reloading last year, all .223REM, cloning the MK262 with good results sub MOA. My barrel is a 20" SS416R and 5R rifling in .223 Wylde, believe it or not, a BCA barrel I call it the unicorn barrel because you all know the bad rap BCA gets with malfunctioning uppers From what ive seen it does like the projectile seated deeper than 2.260, I seat them at 2.250 and use 25.0 of 8208XBR. Now Im fooling around with a 6ARC upper and the learning curve is big. Slowly but surely I'll be there.

Seems hot but if it works more power to you. I had a case head seperation with Win brass after 3 firings with 24.5gr of 8208 under 75gr ELDs loaded way longer than 2.250 for my bolt gun. I have tried both 2.260 and 2.250 in my gas gun, no real difference. I have heard the hornady 75gr ( I have a bunch just for fun plinking) likes to be even shorter than 2.250".

 

[jlorenzo]

Your observation of the temp sensitive of RE-15 is valid and means you are sensitive enough to catch it, which is good. The point of bringing up RE-15 is the reliability of getting it to group well at 24 grains plus or minus a little for each gun, not to switch to it.

Varget is pretty flat temperature wise, but is also known as tipping over on the hot end without much warning. That isn't a worry if you don't load hot to begin with. Roughly 23.5 plus or minus a little trim isn't hot, but 24.5 can be on a bad day.

It does sound like your technique is part of the vertical spread. I would put you on bag riders for a load test to determine the root cause. That gets the rear squeeze bag and bipod out of the question and isolates this to the load and gun if you know how to shoot off bags. If it won't shoot off bags, then you know you have to work the gun or the load. YMMV

If I recall 24.1 was the RL15 spot for me with 77gr SMKs, going to revisit that as well as varget. I have had flat primers with 24.0gr of Varget but they were CCI 200s. I always thought of 24.0gr of Varget as kind of a standard.